It is the aim to define, using the microcalorimeter, along with other instrumentation, significant biochemical reactions which have potential application to clinical practice. Thermodynamic and kinetic values, obtained from the reaction time course curve will be correlated with structural and microenvironment characteristics of membrane-bound ATPase, adenyl cyclase and cholinesterase. Blood cell ATPase (normal and Duchenne muscular dystrophic), blood cell and lymphocyte adenyl cyclase (normal and leukemic) activities will be physically and enzymically characterized. Membrane and soluble cholinesterase interactions with anticholinergics will be studied with relevance to public health problems. Emphasis is upon the use of the intrinsic advantages of the microcalorimeter to understand medically pertinent biochemical reactions as a way to broaden the bases for the eventual development of a higher resolution diagnostic technology. The practical non tedious handling capability of our present instrumentation allows us to resolve the several energetic events that make up the catalyzed sequence. This together with kinetic evaluation computed from the same measurements can offer a more fundamental understanding of events which occur at membrane-cytoplasm interfaces.